A refrigeration cycle apparatus includes, for example, a compressor that compresses and discharges refrigerant. In the case where the compressor is, for example, a scroll compressor or the like, the compressor has a structure in which a refrigerating machine oil is supplied to each sliding portion, such as a bearing for supporting a motor that makes rotational motion, a conversion mechanism portion that converts the rotational motion to oscillatory motion, and a contact surface between an orbiting scroll and a fixed scroll, such that the sliding portion is not worn due to friction. Thus, the refrigerating machine oil is stored in the compressor such that the supply of the refrigerating machine oil is not interrupted.
Here, while the compressor is operating, the refrigerating machine oil flows out via a discharge pipe together with the refrigerant. When the refrigerating machine oil flows out from the compressor, the refrigerating machine oil remains in components that form a refrigerant circuit of the refrigeration cycle apparatus, such as pipes and a heat exchanger. When the refrigerating machine oil within the compressor flows out as described above, the refrigerating machine oil within the compressor may become insufficient, which causes poor lubrication of a compression mechanism portion.
A refrigeration cycle apparatus has been proposed in which a mechanism to separate discharged refrigerating machine oil by an oil separator and return the refrigerating machine oil to the suction side of a compressor is used for preventing poor lubrication of each sliding portion of the compressor. Here, immediately after the compressor is started, the amount of the refrigerating machine oil flowing out from the compressor is increased as compared to that during continuous operation. This is because, immediately after the compressor is started, liquid refrigerant within the compressor rapidly vaporizes to foam, and the refrigerating machine oil flows out together with the refrigerant.
The time of contiguous operation refers to the time during which a preset time period has elapsed and operation of the compressor has been stabilized after the compressor is started, not the time immediately after the compressor is started. It is assumed that even when the oil separator is provided in the refrigeration cycle apparatus, the refrigerating machine oil overflows from the oil separator and flows out through a pipe through which the refrigerant flows.
Thus, as an existing refrigeration cycle apparatus, a refrigeration cycle apparatus has been proposed in which an oil return pipe line opened during continuous operation and an oil return pipe that is mounted on a lower portion of an oil separator, that includes an oil reservoir portion for storing oil during continuous operation, and that is opened during start to return the oil are connected to the oil separator (see, for example, Patent Literature 1). In the refrigeration cycle apparatus disclosed in Patent Literature 1, since the aforementioned oil return pipe line and the oil return pipe including the oil reservoir portion are included, the oil stored in the oil reservoir portion before the time of start easily returns to the suction side, due to a pressure difference, immediately after the start, so that insufficiency of lubricating oil within a compressor is inhibited.